The present invention is directed towards a power module and, more particularly, to a power module which can control the operation of a plurality of relatively high current loads as a function of relatively low current signals generated by a control circuit such as a microprocessor.
A universal power module of the foregoing type is especially useful in connection with the control of major appliances. Such appliances contain a multiplicity of loads, either resistive (e.g., a heater) or inductive (e.g., motors and solenoids) which require currents well in excess of that which can presently be delivered by most integrated circuits. By way of example, such loads require currents up to 40 amps and voltages up to 240 volts. In contrast, the output of a typical integrated circuit will be in the 100 milliamp, 10 volt range. To solve this problem, most prior art appliances utilize mechanical switches and relays to switch on and off respective loads. While such switching circuits are suitable where loads are manually switched on and off by a user of the appliance or automatically switched off by a timer motor, they do not lend themselves to satisfactory use in modern appliances where the appliance loads are controlled electronically by a microprocessor. In such appliances, the microprocessor is capable of generating only relatively weak signals to activate the power switching device. The primary object of the present invention is to provide a universal power module which can switch on and off selected loads of the appliance (or other electronically controlled apparatus) as a function of the relatively low level signals generated by the microprocessor while at the same time providing relatively high currents (e.g., 40 amps) and voltages (e.g., 240 volts) to the load. It is a further major object of the present invention to perform this function in the most efficient, least expensive manner possible.